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| United States Patent |
5,143,632
|
|
Woo
|
September 1, 1992
|
Polysiloxane polymer having pendant aromatic groups useful in enhanced
oil recovery using carbon dioxide flooding
Abstract
A polysiloxane polymer having pendant aromatic groups that is useful in
increasing the viscosity of carbon dioxide. That polymer can be formed by
reacting a polysiloxane containing at least one olefinic group with a
phenyldialkylsilane. That polymer can be used in a method for recovering
oil from an underground oil-bearing earth formation penetrated by an
injection well and a producing well, in which method carbon dioxide is
injected into the formation to displace oil towards the producing well
from which oil is produced to the surface. The viscosity of the carbon
dioxide injected into the formatin is increased at least three-fold by the
presence of a sufficient amount of the polymer and a sufficient amount of
a cosolvent to form a solution of the polymer in the carbon dioxide.
| Inventors:
|
Woo; Gar Lok (Tiburon, CA)
|
| Assignee:
|
Chevron Research and Technology Company (San Francisco, CA)
|
| Appl. No.:
|
669156 |
| Filed:
|
March 14, 1991 |
| Current U.S. Class: |
507/234; 166/268; 166/403; 507/936; 528/15 |
| Intern'l Class: |
E21B 043/22 |
| Field of Search: |
166/268,274,273
252/8.554,8.551
528/15,31,43,28
|
References Cited
U.S. Patent Documents
| 2970150 | Jan., 1961 | Bailey | 528/28.
|
| 4230815 | Oct., 1980 | Itoh et al. | 526/335.
|
| 4427574 | Jan., 1984 | Pierpoint | 528/15.
|
| 4609043 | Sep., 1986 | Cullick | 166/268.
|
| 4701488 | Oct., 1987 | Williams | 524/266.
|
| 4709001 | Nov., 1987 | Maxson | 528/15.
|
| 4913235 | Apr., 1990 | Harris et al. | 166/273.
|
| 4931485 | Jun., 1990 | Inoue et al. | 521/154.
|
| 4945989 | Aug., 1990 | Irani et al. | 166/273.
|
| 4945990 | Aug., 1990 | Irani et al. | 166/273.
|
| 4954401 | Sep., 1990 | Revis | 528/15.
|
| 5022467 | Jun., 1991 | Irani et al. | 166/273.
|
Other References
"Silicon Compounds", PetrarchSystems Silanes & Silicones, 1988-1988.
John L. Speier, "Advances in Organometiallic Chemistry", Catalysis and
Organic Syntheses, vol. 17.
Allen Noshay & James E. McGrath, "Block Copolymers Overview and Critical
Survey", pp. 278-279, Academic Press, Inc.
"Refractors to Silk", Encyclopedia of Chemical Technology, Third Edition,
vol. 20.
|
Primary Examiner: Stoll; Robert L.
Assistant Examiner: Sayala; C.
Attorney, Agent or Firm: Keeling; E. J., Schaal; E. A.
Claims
What is claimed is:
1. A solution comprising carbon dioxide, a polymer, and a cosolvent,
wherein the polymer comprises a polysiloxane polymer having pendant
phenyldialkylsilyl groups; and
wherein the cosolvent is selected from the group consisting of:
(a) alcohols having from 1 to 8 carbon atoms.
(b) aromatics having a single ring and from 6 to 10 carbon atoms.
(c) ketones having from 3 to 10 carbon atoms.
(d) carboxylic acid esters where the carboxylic acid portion has from 2 to
4 carbon atoms and the ester portion has from 1 to 10 carbon atoms.
(e) hydrocarbons having from 2 to 20 carbon atoms, and
(f) ethers and glycol ethers having from 2 to 10 carbon atoms.
2. The solution according to claim 1 wherein the pendant phenyldialkylsilyl
groups are pendant phenyldimethylsilyl groups.
3. The solution according to claim 1 wherein the cosolvent is an aromatic
hydrocarbon having a single ring and from 6 to 10 carbon atoms.
4. The solution according to claim 3 wherein the cosolvent is toluene.
5. In a method for recovering oil from an underground oil-bearing earth
formation penetrated by an injection well and a producing well, in which
method carbon dioxide in injected into the formation to displace oil
towards the producing well from which the oil is produced to the surface,
the improvement comprising injecting into the formation carbon dioxide,
the viscosity of which is increased at least three-fold by the presence of
a sufficient amount of a polysiloxane polymer having pendant
phenyldialkylsilyl groups.
6. The method according to claim 5 wherein the pendant phenyldialkylsilyl
groups are pendant phenyldimethylsilyl groups.
7. The method according to claim 5 wherein a sufficient amount of a
cosolvent is present in the carbon dioxide to form a solution of the
polymer in the carbon dioxide: and
wherein the cosolvent is selected from the group consisting of:
(a) alcohols having from 1 to 8 carbon atoms.
(b) aromatics having a single ring and from 6 to 10 carbon atoms.
(c) ketones having from 3 to 10 carbon atoms.
(d) carboxylic acid esters where the carboxylic acid portion has from 2 to
4 carbon atoms and the ester portion has from 1 to 10 carbon atoms.
(e) hydrocarbons having from 2 to 20 carbon atoms, and
(f) ethers and glycol ethers having from 2 to 10 carbon atoms.
8. The method according to claim 5 wherein the carbon dioxide solution
comprises from 60 to 99.9 weight percent carbon dioxide, from 0.05 to 10
weight percent polymer, and from 0.05 to 40 weight percent cosolvent.
9. The method according to claim 5 in which the carbon dioxide solution is
prepared by forming a first solution of the polymer and the cosolvent and
then mixing carbon dioxide with the first solution.
Description
The present invention relates to a polysiloxane polymer having pendant
aromatic groups; to new compositions of matter comprising carbon dioxide
and a viscosifying amount of a mixture of a cosolvent and that polymer;
and to a method of recovering oil from underground subterranean formations
using those new compositions of matter.
BACKGROUND OF THE INVENTION
In newly discovered oil fields, oil usually will be recovered by the oil
flowing from a producing well under the naturally occurring pressure of
the fluids present in the porous reservoir rocks. That naturally occurring
pressure decreases as the fluids are removed. This phase of production,
called primary production, recovers perhaps 5% to 20% of the oil present
in the formation.
Secondary recovery methods (e.g., waterflooding) are used to recover more
of the oil. In these methods, a fluid is injected into the reservoir to
drive additional oil out of the rocks. Waterflooding has limitations.
Since the water is immersible with oil, as the water displaces the oil the
oil remaining in the reservoir reaches a limiting value known as "the
residual oil saturation" and the oil stops flowing. There is a strong
capillary action which tends to hold the oil in the interstices of the
rocks. The amount of oil recovered by secondary techniques is usually from
about 5% to 30% of the oil initially present.
In recent years, more attention has been directed to enhanced oil recovery
or tertiary recovery methods. These tertiary recovery methods are used to
recover the residual oil by overcoming the capillary forces which trap the
oil during waterflooding. For example, it has been suggested to add
surfactants to the flood to decrease the interfacial tension and thus
allow oil droplets to move to producing wells.
Secondary or tertiary recovery of oil is also possible by the miscible
fluid displacement process. A number of carbon dioxide floods have been
tried in the United States. The carbon dioxide tends to dissolve in the
oil, which swells with a consequent decrease in viscosity and improvement
in the flow to producing wells. The carbon dioxide also extracts light
hydrocarbons from the oil and this mixture of carbon dioxide and light
hydrocarbons can, in some cases, reach a composition that will miscibly
displace the oil.
This carbon dioxide-rich phase characteristically has a lower viscosity
than the oil and tends to finger through the formation. Early carbon
dioxide breakthrough is undesirable since reservoir sweep is reduced and
expensive separation procedures are required to separate and recycle the
carbon dioxide.
In U.S. Pat. No. 4,913,235, Harris et al. report a means of increasing
viscosity for the carbon dioxide thirty-fold or more by using cosolvents,
along with certain defined polymers having a solubility parameter of close
to 6.85 (cal/cc).sup.1/2 [14.0 J.sup.1/2 /cm.sup.3/2 ] and having
electron donor groups such as ether, silyl ether, and tertiary amine.
Those defined polymers include polysiloxanes and polyvinylethers.
SUMMARY OF THE INVENTION
The present invention is based on the discovery that a polysiloxane polymer
having pendant aromatic groups is useful with a cosolvent in increasing
the viscosity of carbon dioxide. Preferably, the pendant aromatic groups
are pendant phenyldialkylsilyl groups, such as phenyldimethylsilyl groups.
Polysiloxane polymers having pendant aromatic groups can be formed by
reacting together a phenyldialkyl silane and a polysiloxane that has at
least one olefinic group, but preferably more than one olefinic group on
the polymer backbone. Preferably, the polymer is formed in the presence of
platinum-containing catalyst, such as chloroplatinic acid or a
platinum-divinyltetramethyldisiloxane complex.
In one embodiment of the present invention, the polymer is used in a method
for recovering oil from an underground oil-bearing earth formation
penetrated by an injection well and a producing well. In that method,
carbon dioxide is injected into the formation to displace the oil towards
the producing well. The viscosity of that carbon dioxide is increased at
least three-fold by the presence of a sufficient amount of the polymer and
a sufficient amount of a cosolvent to form a solution of the polymer in
the carbon dioxide. It is possible that, for some polymers, under some
conditions of pressure and temperature, no cosolvent will be needed.
Usually, the amount of cosolvent needed increases with the molecular
weight of the polymer. Furthermore, the cosolvent requirement is affected
by the field conditions, such as temperature and pressure.
Preferably, the cosolvent is an aromatic hydrocarbon. More preferably, the
cosolvent is toluene.
Preferably, the carbon dioxide solution comprises from 60 to 99.9 weight
percent carbon dioxide, from 0.05 to 10 weight percent polymer, and from
0.05 to 40 weight percent cosolvent. The carbon dioxide solution can be
prepared by forming a solution of the polymer and the cosolvent and then
mixing carbon dioxide with the polymer-cosolvent solution.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In its broadest aspect, the present invention is based upon the discovery
of a polysiloxane polymer having pendant aromatic groups that is soluble
in carbon dioxide in the presence of a cosolvent.
In one preferred embodiment of this invention, this polymer is used in a
method for recovering oil from an underground oil-bearing earth formation
penetrated by an injection well and a producing well. In that method,
carbon dioxide is injected into the formation to displace the oil towards
the producing well. The viscosity of the carbon dioxide that is injected
into the formation is increased at least three-fold by the presence of a
sufficient amount of a polysiloxane polymer having pendant aromatic groups
and a sufficient amount of a cosolvent to form a solution of the polymer
in the carbon dioxide. It is possible that, for some polymers, under some
conditions of pressure and temperature, no cosolvent will be needed.
POLYMER
The polymer of the present invention is a polysiloxane polymer having
pendant aromatic groups. By "polysiloxane polymer having pendant aromatic
groups," we mean linear polydialkylsiloxanes, which have aromatic groups
linked to some of the alkyl groups in the polymer, for example by silicone
bridges. Preferably, the pendant aromatic groups are phenyldimethylsilyl
groups and the alkyl groups have one to ten carbons.
A polysiloxane polymer having pendant aromatic groups can be formed by
reacting a polysiloxane containing at least one olefinic group with a
phenyldialkyl silane in the presence of platinum-containing catalyst. For
instance, in one set of runs, Me.sub.3 SiO[(SiMe.sub.2 O).sub.80
(SiCH.dbd.CH.sub.2 MeO).sub.20 ].sub.x SiMe.sub.3 (300,000 centistokes)
was reacted with phenyldimethylsilane.
TABLE A
__________________________________________________________________________
Polysiloxane Silane SiH:
SiCH.dbd.CH.sub.2,
SiH,
SiCH.dbd.CH.sub.2
Catalyst
Toluene
Run
g Mole g Mole
Mole Ratio
Type.sup.2
.mu.l
g
__________________________________________________________________________
I 8.0
0.0184 2.78
0.0204
1.1 H.sub.2 PtCl.sub.6
10 39.9
II 16.0
0.0368 0.54
0.0397
1.1 H.sub.2 PtCl.sub.6
3 8.2
III
12.2
0.0280 3.00
0.0221
0.8 PC072
5 17.2
IV 8.0
0.0184 2.73
0.0201
1.1 H.sub.2 PtCl.sub.6
15 43.2
V 8.0
0.0184 2.73
0.0201
1.1 PC072
12 43.2
VI 8.0
0.0184 2.75
0.0202
1.1 H.sub.2 PtCl.sub.6
20 40.1
VII
8.0
0.0184 2.91
0.0214
1.2 H.sub.2 PtCl.sub.6
20 16.3
VIII
32.0
0.0736 10.80
0.0794
1.1 H.sub.2 PtCl.sub.6
50 172.3
IX 32.0
0.0736 10.80
0.0794
1.1 PC072
.sup. 80.sup.1
171.2
__________________________________________________________________________
.sup.1 in two portions.
.sup.2 H.sub.2 PtCl.sub.6 is 0.1 M in isopropyl alcohol; PC072 is platinu
divinyltetramethyldisiloxane complex in xylene (neutral, 2-3% Pt). PC072
is a product identification number of Petrarch Systems.
The viscosity of carbon dioxide at 2500 psi and 54.degree. C. was increased
about six fold by using 2% polymer of run VIII and 30% toluene.
TABLE B
__________________________________________________________________________
Viscosity of Product.sup.1 in
Reaction Conditions
Toluene, cST at 25.degree. C.
Temp.
Time
Reactant
2 g 3 g
Run
.degree.C.
Hr.
Conc. Wt %
Prod/100 ml
Prod/100 ml
Comments
__________________________________________________________________________
I RT 0.0
21.3 1.307
72-76
2.0 2.360 4.100 Reacted
II 70-92
2.2
20.7 4.130 Reacted
III
RT 16.0
46.9 No change
85 0.8 gel
IV RT .0 19.9 1.321
70 2.3 2.671
70 5.0 3.066
V 70 2.3
19.9 2.924
70 5.0 3.339
VI 100-105
5.0
21.1 27.59 Some gel
VII
90-105
4.0
40.1 Gel
VIII
80-87
6.5
19.6 3.668 6.261 *4.946 cST at 2.5 g/100 ml
IX 80-87
13.0
19.7 4.736 7.632 *6.302 cST at 2.5 g/100
__________________________________________________________________________
ml
*1% Ph.sub.3 P used to stop reaction
.sup.1 Assumed complete reaction, product not isolated
CARBON DIOXIDE
The carbon dioxide can come from any suitable source, such as those
described in "Miscible Displacement" by Fred I. Stalkup, Jr. (Monograph
Vol. 8, Henry L. Doherty Series, ISBN NO895203197, Society of Petroleum
Engineers, 1983, Chap. 8, sec. 8.4). Substantially pure carbon dioxide is
preferred, but water-saturated carbon dioxide is acceptable since water
(or brine) is usually present in the formation. Usually, the carbon
dioxide contains at least 95% carbon dioxide and preferably at least 98%
carbon dioxide, the remainder being usually light hydrocarbons. The amount
of impurities in the carbon dioxide which can be tolerated is a function
of the type of oil to be displaced and the type of displacement operation.
COSOLVENT
As a class, it would appear that many materials are suitable for use as
cosolvents in this invention:
(a) alcohols having from 1 to 8 carbon atoms,
(b) aromatics having a single ring and from 6 to 10 carbon atoms,
(c) ketones having from 3 to 10 carbon atoms,
(d) carboxylic acid esters where the carboxylic acid portion has from 2 to
4 carbon atoms and the ester portion has from 1 to 10 carbon atoms,
(e) hydrocarbons having from 2 to 20 carbon atoms, including refinery
streams such as naphthas, kerosene, gas oils, gasolines, etc., and
(f) ethers and glycol ethers having from 2 to 10 carbon atoms.
If hydrocarbons are used, preferably they are aliphatic, naphthenic, or
aromatic hydrocarbons having from 3 to 10 carbon atoms. More preferably,
the cosolvent is an aromatic hydrocarbon. Most preferably, the cosolvent
is toluene.
One technique for obtaining the desired cosolvent on site is to contact the
carbon dioxide in a liquid-liquid extraction apparatus with recovered
crude or a fraction of such crude for a sufficient time to permit the
carbon dioxide to extract enough light hydrocarbons to function as the
cosolvent. The desired amount of polymer would then be added to the carbon
dioxide-light hydrocarbon extent to form the oil-driving material.
The polymer-cosolvent-carbon dioxide mixture must be compatible with the
formation fluids so that the polymer won't precipitate in the formation
after injection.
AMOUNTS OF CARBON DIOXIDE, POLYMER, AND COSOLVENT
The new compositions of this invention preferably comprise from 60 to 99.9
weight percent carbon dioxide and a sufficient amount of a mixture of a
polymer and a cosolvent to effect at least a three-fold increase in the
viscosity of the carbon dioxide. Usually the weight percent polymer in the
mixture is from 0.05 to 10 weight percent. The amount of cosolvent is at
least sufficient to dissolve the desired amount of polymer in the carbon
dioxide. This amount of cosolvent is usually from 0.05 to 40 weight
percent of the final mixture.
One method of preparing the viscous carbon dioxide solution is by forming a
first solution of the polymer and cosolvent and then mixing carbon dioxide
with the polymer-cosolvent solution. The viscous carbon dioxide is
displaced through the formation by a drive fluid which is comprised of
slugs of viscous carbon dioxide alternated with slugs of a fluid
comprising water or reservoir brine.
While the present invention has been described with reference to specific
embodiments, this application is intended to cover those various changes
and substitutions which may be made by those skilled in the art without
departing from the spirit and scope of the appended claims.
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